TWI498272B - Microelectromechanical system device and manufacturing method thereof - Google Patents

Description

Microelectromechanical system device and method of manufacturing same

The invention relates to a microelectromechanical system, in particular to a diaphragm having a composite layer structure formed by at least a first polysilicon layer, an intermediate layer and a second polysilicon layer, which is resistant to acid damage during release of the structure, and The MEMS membrane of the composite layer structure formed by the stress can cancel each other out, so that it has a low structural stress, and is relatively stable and is not susceptible to temperature and humidity, and has reliability problems such as cracking and creeping. Production method.

Microelectromechanical Systems (MEMS), commonly referred to as MEMS, is an industrial technology that integrates microelectronics and mechanical technology. MEMS is a micron-sized mechanical system that includes a movable structure that can be fabricated. Electronic components, such as microphones, gyroscopes, pressure gauges, RF switchers, etc., have different mechanisms for receiving gravity, electromagnetic waves, pressure, sound waves, etc. to generate electronic signals and transmit them.

The fabrication of these tiny active structures on semiconductor materials cannot be easily achieved by conventional semiconductor processes or instruments. Fabric fabrication of MEMS fabs typically requires DRIE (deep reactive ion etching) equipment using deep ion etching. The way to create a floating active structure, for example: in a MEMS microphone, this structure is generally called a diaphragm.

Because MEMS microphones have many advantages, such as small size, easy design and integration, good sound quality, stable performance and are not susceptible to mechanical vibration, temperature changes, electromagnetic interference, so on mobile phones, headphones, notebook computers (NB), cameras and other equipment. The Electric Condenser Microphone (ECM) has been gradually replaced.

With the rapid development of mobile communications in recent years, the global hot sale of smart phones has also made wisdom The market for micro-electromechanical systems (MEMS) microphones equipped with mobile phones is promising; according to market research organizations, global MEMS microphone shipments will grow from 441 million in 2009 to more than 1.7 billion in 2014. Market research firm iSuppli predicts that by 2014, most smartphones will use more than two MEMS microphones, and handheld devices and notebooks will remain the largest applications for MEMS microphones. While MEMS microphones are much more expensive than ECMs, iSuppli says MEMS microphones have advantages in size, scalability, temperature stability, and sound quality. The smart phone uses two independent MEMS microphones to suppress noise, which reduces the background sound to enhance the clarity of the voice call.

Existing CMOS MEMS devices typically include CMOS circuits and MEMS devices that are fabricated on the same substrate by semiconductor fabrication techniques, and are primarily utilized for MEMS devices with sensing diaphragms (eg, as microphone diaphragms or other applications). The etching technique etches the dielectric and the substrate made of tantalum, as shown in the ninth figure, which is a schematic diagram of the implementation of the prior art MEMS device 6. As is clear from the figure, when the dielectric 62 is formed on the substrate After the 61 is over, the substrate 61 and the dielectric layer 62 need to be etched to form an opening 63, and a cavity 66 is formed between the back plate structure 64 and the diaphragm 65. The back plate structure 64 forms a plurality of openings. The through holes 67 communicating with the cavity 66 thereby exposing the diaphragm 65 so that the diaphragm 65 can be sensed.

Wherein, the diaphragm 65 is partially formed by metal sputtering aluminum to form a mesh structure, and after the final diaphragm 65 is released, a polymer material is deposited to cover the metal aluminum diaphragm to close the screen. The mesh structure, but the diaphragm 65 has the following problems:

1. Polymer materials are non-semiconductor IC process materials, so additional machines are required. Production, and it will pollute the clean room of the fab.

Second, because the microelectromechanical system is a micron-sized mechanical system, including the system produced by three-dimensional lithography of various shapes and different shapes, and the size is usually between micrometers and millimeters. Under such a range of sizes, the physics of daily life Experience is often not applicable, and the composite diaphragm made of metal-sputtered aluminum and polymer is very susceptible to temperature and humidity, especially when the polymer is easy to absorb moisture and cause material degradation under long-term action. Therefore, reliability problems such as rupture and creep have occurred in the market.

Third, the through hole (acoustic hole) and cavity (back air cavity) of the microphone are complicated and cannot be completed at the fab, but must be transferred to a professional MEMS foundry to complete the through hole, cavity and vibration after completing the CMOS process. The film release process, because it must first etch the dielectric layer DRIE and the via silicon DRIE on the front side of the wafer, and then use a special bonding device to bond the front side of the wafer to a dedicated carrier wafer. The step is easy to damage the microphone diaphragm, and then flipped to the crystal back to make the cavity, and then remove the carrier wafer, so this method will pollute the fab in addition to the higher cost.

4. As the scale of MEMS products shrinks and the surface area to volume ratio increases, the micro-electromechanical systems generated by micro-machining technology are prone to stiction problems. Attachments are various types of MEMS such as microphones. The main reason for the failure of products such as gyroscopes. The reasons can be summarized as follows:

(1) The oxide after the microfabrication technique must be removed by etching, and the remaining residue is removed using a solution. The water droplets formed after cleaning cause adhesion of the diaphragm of the MEMS due to surface tension and capillary action.

(2) When the static charge is unbalanced, the diaphragm is biased to one side due to the repulsion of static electricity.

In view of the above problems, it has been proposed for the diaphragm portion to use metal sputtered aluminum and oxide to form a diaphragm. However, it also has the following problems:

First, the diaphragm made of metal sputtered aluminum is very susceptible to temperature, so it is easy to cause the sensitivity of the microphone to drift.

Second, the diaphragm made of metal sputtered aluminum is very easy to be damaged by acid when it is released.

3. The through hole and cavity of the microphone are formed by the base of the crucible. Although it can be completed at the fab, the cost is too high due to the complicated process (the yellow light step is too much and the DRIE time is too long).

Therefore, how to solve the above problems and deficiencies in the above-mentioned applications, that is, the inventors of the present invention and those involved in the industry are eager to study the direction of improvement.

Therefore, in view of the above-mentioned deficiencies, the inventors of the present invention have collected relevant materials, and have evaluated and considered such patents through continuous evaluation and modification through multi-party evaluation and consideration, and through years of experience in the industry.

A first object of the present invention is to provide a microelectromechanical system device in which a diaphragm of a composite layer structure is formed by a first polysilicon layer, an intermediate layer, and a second polysilicon layer.

In order to achieve the above object, a MEMS device includes at least one body having an opening at a predetermined position, including a substrate and a dielectric layer disposed on the substrate; a diaphragm disposed at the opening And the two ends are supported by the body, and include a first polysilicon layer, an intermediate layer and a second polysilicon layer, wherein the intermediate layer is disposed on the first polysilicon layer, the second polycrystalline layer The enamel layer is disposed on the intermediate layer; and a back plate structure is disposed at the opening, the two ends are fixed by the body, and the back plate structure is opened A plurality of through holes are formed, and a cavity communicating with the through hole is formed between the diaphragm and the diaphragm.

In a preferred embodiment, the substrate is a tantalum substrate.

In a preferred embodiment, the dielectric layer has a CMOS circuit.

In a preferred embodiment, both ends of the backplane structure are held by the dielectric layer and disposed above the diaphragm.

In a preferred embodiment, the backplane structure includes a first metal layer, an insulating layer, and a second metal layer. The insulating layer is disposed on the first metal layer and is covered with metal and protects the The insulating layer prevents the insulating layer from being damaged by the acid solution when the structure is released, and the second metal layer is disposed on the insulating layer.

In a preferred embodiment, the backing plate structure is between the cavities and includes a recess or a bump.

In a preferred embodiment, the diaphragm surface has a corrugated or textured structure to reduce the diaphragm stress.

A second object of the present invention is to provide a method of fabricating a microelectromechanical system device that forms a diaphragm of a composite layer structure with a first polysilicon layer, an intermediate layer, and a second polysilicon layer.

In order to achieve the above object, a method for fabricating a microelectromechanical system device according to the present invention comprises at least the steps of: providing a substrate; forming a diaphragm comprising: forming a first polysilicon layer in a portion of the substrate; forming an intermediate layer On the first polysilicon layer; and forming a second polysilicon layer on the intermediate layer; forming a dielectric layer on the second polysilicon layer and the substrate; Forming a back plate structure on the dielectric layer; and etching the substrate and the dielectric layer to a predetermined position to form an opening to expose the diaphragm at the opening and between the back plate structure and the diaphragm A cavity is formed, the back plate structure forming a plurality of through holes communicating with the cavity.

In a preferred embodiment, the forming a backplane structure on the dielectric layer further includes the steps of: forming a first metal layer on the dielectric layer; forming an insulating layer on the first metal layer, and using a metal The insulating layer is coated and protected to prevent the insulating layer from being damaged by the acid solution when the structure is released; and a second metal layer is formed on the insulating layer.

In a preferred embodiment, the gap between the back plate structure and the diaphragm is formed, and the back plate structure is formed between the cavities by etching to form a cavity or a convex portion. Piece.

Wherein, the diaphragm used in the present invention comprises the first polysilicon layer, the intermediate layer and the second polysilicon layer to form a diaphragm of the composite layer structure, thereby being resistant to acid when the structure is released. The damage of the liquid, and the diaphragm of the composite layer structure formed by the same can be offset by the stress, so it has a low structural stress, and is relatively stable and is not susceptible to temperature and humidity and reliability problems such as cracking and creeping.

Moreover, the MEMS device of the present invention can adopt the standard CMOS process of the general foundry of the industry, and can completely integrate the MEMS structure according to the semiconductor process rules and materials, and integrate it into the CMOS component, so that it is better. Cost-effectiveness.

Furthermore, the present invention utilizes a crucible substrate to form a cavity, so that the process is simple and has a relatively low cost. The present invention does have practical advancement by the foregoing structure and efficacy.

In addition, the present invention also utilizes standard materials of semiconductors to prevent anti-stiction. The product fails when it is released for structural release and is reliably measured for high temperature and high humidity. It is formed between the cavities by etching to form pits or bumps, and a composite film is deposited on the pits or bumps to form a small contact area, which avoids van der Waals force or electrostatic adsorption.

In order to achieve the above objects and effects, the technical means and the structure of the present invention will be described in detail with reference to the preferred embodiments of the present invention.

Referring to the first embodiment, which is a cross-sectional view of a preferred embodiment of the present invention, it is clear from the figure that a MEMS device 1 of the present invention includes at least a body 2, a diaphragm 3, and A backing plate structure 4. In the present embodiment, the MEMS device 1 of the present invention is a MEMS microphone, but is not limited thereto. The invention can be applied to a Microelectromechanical Systems (MEMS) related structure including an accelerometer, a gyroscope, a pressure gauge, and the like.

The body 2 is provided with an opening 21 at a predetermined position thereof, and includes a substrate 22 and a dielectric layer 23 disposed on the substrate 22. The substrate 22 is a germanium substrate 22 having a CMOS circuit 5 therein.

The diaphragm 3 is disposed at the opening 21, and the two ends are supported by the body 2, and includes a first polysilicon layer 31, an intermediate layer 32 and a second polysilicon layer 33. The intermediate layer 32 is disposed on On the first polysilicon layer 31, the second polysilicon layer 33 is disposed on the intermediate layer 32. The surface of the diaphragm 3 has a corrugated or grain structure to reduce the stress of the diaphragm 3, and may have better sensitivity. The intermediate layer 32 may be formed of a non-metal material such as tantalum nitride or an oxide layer.

The back plate structure 4 is disposed at the opening 21 , and the two ends are fixed by the body 2 . The back plate structure 4 defines a plurality of through holes 41 , and a contact with the diaphragm 3 forms a communication with the through hole 41 . Cavity 42. In this embodiment, the two ends of the backplane structure 4 are held by the dielectric layer 23 and disposed on the Above the diaphragm 3, the backplane structure 4 includes a first metal layer 43, an insulating layer 44, and a second metal layer 45. The insulating layer 44 is disposed on the first metal layer 43 and is wrapped with metal. The insulating layer 44 is covered and protected from the acid solution when the structure is released, and the second metal layer 45 is disposed on the insulating layer 44.

It should be noted that the back plate structure 4 is between the cavities 42 and can be formed by etching to form a cavity or a bump. In this embodiment, the bump 46 is formed on the cavity or the bump 46. The composite film is deposited to form a small contact area, which avoids the vane force or electrostatic adsorption of the diaphragm 3. Wherein, the outermost layer material of the composite film needs to be an insulating material and the composite layer which is resistant to acid etching (relative to the material to be etched by the acid solution) when the structure is released does not need to be an insulating material but must be capable of blocking the acid etching of the backing plate structure. 4 or diaphragm 3.

Please refer to the second embodiment to the eighth embodiment, which are flowcharts of the preferred embodiment of the present invention and the first to sixth embodiments. It can be clearly seen from the figure that the microelectromechanical system device manufacturing method of the present invention is In the embodiment, the manufacturing method of the MEMS device of the present invention is a MEMS microphone manufacturing method, but is not limited thereto. The invention can be applied to a micro electromechanical system (MEMS) related manufacturing method including an accelerometer, a gyroscope, a pressure gauge, etc., and at least comprises the following steps: (110) providing a substrate 22; (120) forming a diaphragm 3, The method comprises: (121) forming a first polysilicon layer 31 in a partial region of the substrate 22; (122) forming an intermediate layer 32 on the first polysilicon layer 31; and (123) forming a second polycrystal a germanium layer 33 is on the intermediate layer 32; (130) a dielectric layer 23 is formed on the second polysilicon layer 33 and the substrate 22; (140) forming a backplane structure 4 on the dielectric layer 23; and (150) etching the substrate 22 and the dielectric layer 23 to a predetermined position to form an opening 21 to expose the diaphragm 3 at the opening 21 And forming a cavity 42 between the back plate structure 4 and the diaphragm 3, the back plate structure 4 forming a plurality of through holes 41 communicating with the cavity 42.

In this step (110), a substrate 22 which is commonly used in a general semiconductor process is provided.

In the step (120), at least one stop layer (also referred to as a buffer layer) (not shown) is formed on the substrate 22 before forming a diaphragm 3, which can be protected when etching is performed. Diaphragm 3. And after forming the stop layer, at least one sacrificial layer (not shown) is formed on the stop layer and the substrate 22. The commonly used materials of the sacrificial layer are mainly tantalum oxide, tantalum nitride, photoresist, etc. The effect of the sacrificial layer is that during the formation of the movable microstructure member (in the present invention, the diaphragm 3), the material is first deposited on the outer surface of the desired microstructure member, and then the chemical etchant is used to The sacrificial layer film is etched away without damaging the microstructured parts.

Moreover, the diaphragm 3 of the present invention includes the steps (121), (122), and (123), and the diaphragm 3 includes the first polysilicon layer 31, the intermediate layer 32, and the second polysilicon layer. a composite layer structure formed by 33, forming a first polysilicon layer 31 in a partial region of the substrate 22 from bottom to top, forming the intermediate layer 32 on the first polysilicon layer 31, and forming the A second polysilicon layer 33 is on the intermediate layer 32. The intermediate layer 32 may be formed of a non-metal material such as tantalum nitride or an oxide layer.

In the step (130), a dielectric layer 23 is formed on the second polysilicon layer 33 and the substrate 22, and during the process of forming the dielectric layer 23, a CMOS circuit 5 is formed on the dielectric layer 23. in.

In the step (140), during the process of forming the dielectric layer 23, a back junction is formed. The formation of the backing plate structure 4 further includes the steps of: forming a first metal layer 43 on the dielectric layer 23, forming an insulating layer 44 on the first metal layer 43, and The insulating layer 44 is covered and protected by metal to prevent the insulating layer 44 from being damaged by the acid solution when the structure is released, and a second metal layer 45 is formed on the insulating layer 44. The backplane structure 4 is a three-layer stacked structure.

In the step (150), the substrate 22 and the dielectric layer 23 are etched to form an opening 21. Generally, the MEMS device 1 includes a CMOS region and a MEMS region at the opening 21. It is the MEMS area, and its part is the CMOS area. The sacrificial layer and the stop layer under the diaphragm 3 are removed by an etching technique, so that the diaphragm 3 is exposed to the opening 21, and a cavity is formed between the back plate structure 4 and the diaphragm 3. 42. The backing plate structure 4 forms a plurality of through holes 41 communicating with the cavity 42.

It should be particularly noted that a cavity 42 is formed between the back plate structure 4 and the diaphragm 3, and the back plate structure 4 is disposed between the cavity 42 and can be formed by etching to form a cavity or a bump. In the present embodiment, the bump 46 is formed, and a composite film is deposited on the cavity or the bump 46 to form a small contact area, and the diaphragm 3 or the electrostatic adsorption effect can be avoided. Wherein, the outermost layer material of the composite film needs to be an insulating material and the composite layer which is resistant to acid etching (relative to the material to be etched by the acid solution) when the structure is released does not need to be an insulating material but must be capable of blocking the acid etching of the backing plate structure. 4 or diaphragm 3.

Referring to the drawings, the present invention has the following advantages over conventional techniques:

1. The diaphragm 3 of the composite layer structure of the first polycrystalline germanium layer 31, the intermediate layer 32 and the second polycrystalline germanium layer 33 of the present invention has a lower structural stress due to the stresses canceling each other out, and a diaphragm 3 capable of resisting the destruction of the acid upon release of the structure and forming a composite layer structure It is more stable and less susceptible to temperature and humidity and reliability problems such as rupture and creep.

2. The present invention is compatible with existing semiconductor processes, has high performance and lowest cost, and the MEMS microphone fabricated by using the MEMS device 1 of the present invention and the manufacturing method thereof has better cost effectiveness and can be suppressed Noise.

Third, the use of the crucible substrate to form a cavity, so the process is simple and has a lower cost.

4. The present invention has an anti-stiction structure that avoids van der Waals forces or electrostatic adsorption.

Through the above detailed description, it can fully demonstrate that the object and effect of the present invention are both progressive in implementation, highly industrially usable, and are new inventions not previously seen on the market, and fully comply with the invention patent requirements. , 提出 apply in accordance with the law. The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the invention. All changes and modifications made in accordance with the scope of the invention shall fall within the scope covered by the patent of the invention. I would like to ask your review committee to give a clear explanation and pray for it.

(this invention)

1‧‧‧Micro-Electromechanical System Installation

2‧‧‧ Ontology

21‧‧‧ openings

22‧‧‧Base

23‧‧‧Dielectric layer

3‧‧‧ Diaphragm

31‧‧‧First polycrystalline layer

32‧‧‧Intermediate

33‧‧‧Second polysilicon layer

4‧‧‧ Backplane structure

41‧‧‧through hole

42‧‧‧ cavity

43‧‧‧First metal layer

44‧‧‧Insulation

45‧‧‧Second metal layer

46‧‧‧Bumps

5‧‧‧ CMOS circuit

(previous technology)

6‧‧‧Microelectromechanical system devices

61‧‧‧Base

62‧‧‧Dielectric

63‧‧‧ openings

64‧‧‧Backplane structure

65‧‧‧Densor

66‧‧‧ Cavity

67‧‧‧through hole

BRIEF DESCRIPTION OF THE DRAWINGS The first drawing is a cross-sectional view of a preferred embodiment of the invention illustrating the MEMS device of the present invention.

The second drawing is a flow chart of a preferred embodiment of the present invention, illustrating a method of fabricating a MEMS device of the present invention.

The third embodiment is a schematic diagram of a preferred embodiment of the present invention, illustrating a method of fabricating a microelectromechanical system device of the present invention, and providing a substrate.

The fourth embodiment is a schematic diagram of the implementation of the preferred embodiment of the present invention. The method for fabricating the MEMS device of the present invention is described to form a diaphragm.

The fifth embodiment is a schematic diagram of the implementation of the preferred embodiment of the present invention. The method for fabricating the MEMS device of the present invention is to form a dielectric layer on the second polysilicon layer and the substrate.

Figure 6 is a schematic view of a preferred embodiment of the present invention, illustrating a method of fabricating a microelectromechanical system device of the present invention, forming a backplane structure on the dielectric layer.

7 is a schematic diagram of a preferred embodiment of the present invention, illustrating a method of fabricating a MEMS device of the present invention, etching a predetermined position of the substrate and the dielectric layer to form an opening to expose the diaphragm At the opening.

The eighth embodiment is a schematic diagram of a preferred embodiment of the present invention. The method for fabricating the MEMS device of the present invention is such that a cavity is formed between the back plate structure and the diaphragm, and the back plate structure forms a plurality of connections. a through hole of the cavity.

The ninth diagram is a schematic diagram of the implementation of the prior art MEMS device.

1‧‧‧Micro-Electromechanical System Installation

2‧‧‧ Ontology

21‧‧‧ openings

22‧‧‧Base

23‧‧‧Dielectric layer

3‧‧‧ Diaphragm

31‧‧‧First polycrystalline layer

32‧‧‧Intermediate

33‧‧‧Second polysilicon layer

4‧‧‧ Backplane structure

41‧‧‧through hole

42‧‧‧ cavity

43‧‧‧First metal layer

44‧‧‧Insulation

45‧‧‧Second metal layer

46‧‧‧Bumps

5‧‧‧ CMOS circuit

Claims (10)

A MEMS device includes at least a body having an opening at a predetermined position, including a substrate and a dielectric layer disposed on the substrate; a diaphragm disposed at the opening, the two ends being through the body Holding, comprising a first polysilicon layer, an intermediate layer and a second polysilicon layer, the intermediate layer is disposed on the first polysilicon layer, and the second polysilicon layer is disposed on the intermediate layer And a back plate structure disposed at the opening, the two ends are held by the body, the back plate structure is provided with a plurality of through holes, and a cavity communicating with the through hole is formed between the back plate and the diaphragm. The MEMS device of claim 1, wherein the substrate is a ruthenium substrate. The MEMS device of claim 1, wherein the dielectric layer has a CMOS circuit. The MEMS device of claim 1, wherein the two ends of the backplane structure are held by the dielectric layer and disposed above the diaphragm. The MEMS device of claim 4, wherein the backplane structure comprises a first metal layer, an insulating layer and a second metal layer, the insulating layer is disposed on the first metal layer, and The insulating layer is covered and protected by metal to prevent the insulating layer from being damaged by the acid solution when the structure is released, and the second metal layer is disposed on the insulating layer. The MEMS device of claim 1, wherein the back plate structure comprises a cavity or a bump between the cavities. The MEMS device of claim 1, wherein the diaphragm surface has a corrugated or grain structure to reduce the diaphragm stress. A method for fabricating a microelectromechanical system device, comprising at least the steps of: providing a substrate; forming a diaphragm comprising: forming a first polysilicon layer on the portion of the substrate; forming an intermediate layer on the first polysilicon layer And forming a second polysilicon layer on the intermediate layer; forming a dielectric layer on the second polysilicon layer and the substrate; forming a backplane structure on the dielectric layer; and etching the substrate Presetting a position with the dielectric layer to form an opening to expose the diaphragm at the opening, and forming a cavity between the back plate structure and the diaphragm, the back plate structure forming a plurality of communicating with the cavity Through hole. The method of fabricating a MEMS device according to claim 8, wherein the forming a back plate structure on the dielectric layer further comprises the steps of: forming a first metal layer on the dielectric layer; forming an insulating layer. And covering the first metal layer with a metal to protect the insulating layer from the acid solution when the structure is released; and forming a second metal layer on the insulating layer. The method of fabricating a microelectromechanical system device according to claim 8, wherein the method further comprises: forming a cavity between the back plate structure and the diaphragm, further comprising: etching the back plate structure between the cavities by using etching In a manner, a recess or a bump is formed.